This invention relates to rotor structures for three-phase synchronous permanent-magnet motor specifically used as motors or electric power generators and, more particularly, to a rotor structure, for a permanent-magnet motor, which has an increased strength to restrict deformation of the rotor structure caused at a high speed and which is specifically suited for an electric motor or an electric power generator of an electric vehicle.
A current permanent-magnet motor has achieved an extremely high operating performance to be suited for use in an automotive vehicle and has been already put to practical use. Also, it has been a usual practice to employ the permanent-magnet motor as an auxiliary propelling motor in a hybrid type electric vehicle. Thus, it is known that the permanent-magnet motor has an excellent operating characteristic among other electric motors. However, the permanent-magnet motor has many other remaining technical matters to be solved, and a still further development over the existing permanent-magnet motor is expected to solve the above technical matters to provide a further improved operating performance.
Typical examples of the above-mentioned technical matters involve a miniaturization of the motor for a reduced space, and a property of high speed rotation of the motor to realize one of various expedients to provide a high output performance. In a latter case where the motor rotates at an extremely high speed of more than 10,000 rpm, it is required for the rotor structure to have an extremely high strength.
FIG. 1 shows a typical example of a rotor structure for a permanent-magnet motor of a related art. The rotor structure is constructed having a pair of axially spaced annular end plates 1, 1, and an annular laminated stack 2 of electromagnetic sheets. The annular laminated stack 2 and the annular end plates 1, 1 are fixedly supported with a cylindrical core buck 3 of the cylindrical core buck 3, which is connected to a rotor shaft 5 via a connecting portion 6 for rotating movement therewith. As viewed in FIG. 2, the annular laminated stack 2 has plural permanent magnets 4, 4 located at circumferentially, equally spaced positions. While, in FIG. 2, only a single pole for the permanent magnets 4, 4 is shown, it is to be noted that the motor shown in FIGS. 1 and 2 is of the type having eight poles. The motor also has a magnet retaining structure wherein the magnet for one pole is divided into two pieces, with a central portion of one pole forming a bridge configuration to provide the magnet retaining structure having an increased strength to resist the centrifugal force.
In the permanent-magnet motor shown in FIG. 1, however, it is further required that the rotor structure should be improved to provide a further increased durability and strength in order to meet the need for the high output performance and the property of high speed rotation required in recent years. Also, it is required for the rotor structure to be manufactured in a simplified process to provide a structure having a high reliability without the use of an electronic beam welding technique that requires a high skill.
The present invention has been made to address the above technical matters and has an object to provide a rotor structure, for a permanent-magnet motor, which ensures an increased strength and durability even at high speed rotation and which has a structure enabled to be manufactured without the use of a highly skilled fabricating technique such as an electronic beam welding technique.
It is extremely difficult for the rotor structure to ensure a high reliability in restricting deformation, of the rotor structure caused at high speed rotation, with the use of the welding technique. Research and development have been deeply made with a view to finding out a new and unique joining structure of the rotor structure that can disenable the use of the welding technique. As a result, a new rotor structure is found wherein deformation of annular end plates of the rotor structure is restricted at the high speed rotation with the use of a unique mechanical fixing structure.
According to an aspect of the present invention, there is provided a rotor structure for a permanent-magnet motor, which comprises an annular laminated stack of electromagnetic steel sheets incorporating therein a permanent magnets, a pair of annular end plates between which the annular laminated stack is sandwiched, a cylindrical core buck having its outer circumferential periphery carrying thereon the annular laminated stack and the annular end plates, and a rotor shaft integrally connected to the cylindrical core buck to be rotatable therewith. Each outer end surface of the annular laminated stack has a plurality of first contoured fixing portions, and an inner surface of each of the annular end plates has a plurality of second contoured fixing portions. The annular laminated stack and the annular end plates are fixedly coupled to one another by caulking at the first and second fixing portions.
According to a second aspect of the present invention, there is provided a rotor structure for a permanent-magnet motor, which comprises an annular laminated stack of electromagnetic steel sheets incorporating therein permanent magnets, annular means holding the annular laminated stack at both sides thereof in a fixed place, cylindrical means carrying thereon the annular laminated stack and the annular means, and a rotor shaft integrally connected to the cylindrical means to be rotatable therewith. Each outer end surface of the annular laminated stack has a plurality of first contoured fixing portions, and the annular means has a plurality of second contoured fixing portions. The annular laminated stack and the annular means are fixedly coupled to one another by caulking at the first and second fixing portions.